Marcelianus Adam

Adam is a character in MPST who served as an antagonist in season 1 and tritagons n season 2 and 2.5, as well as a supporting character in the third season of Zero Tolerance. Despite Adam having bully instincts due to him hanging out with Hansen and Armin, he could see things the other two couldn't, which is putting a limit to doing crazy stuffs such as violence, as a proof that Adam decided to unfriend Armin after seeing him beating down Kevin and almost killed him. He's known as a redeemed character between season 1 and season 2.

Personality
In season 1, he's simply being much of a bully, but unlike the other two, he's not insane, but he's rather calm. When Armin had hit the fan (or in this case, beating Kevin a lot of times), he started to have a change of heart and decided to unfriend Armin.

In season 2, he's started to become a really nice person, despite him doing or saying things that could be a bit offensive. Despite this, Adam could realize the attitude that's still sticking to him (the bad ones), whether Andrew pointed it out or not. He's even willing to step-up and stop the fight when he saw Nate in the middle of the field fighting bullies, despite him being knocked down afterwards.

Armin
They had great friendship relationship until the time when Kevin and Armin had a fought in class. Due to Armin's insane way of beating Kevin, Adam thought of Armin as somewhat too crazy, and decided to not hang out with him again.

In season 2, Adam's trust towards Armin's completely gone, where he's even willing to fight Armin despite Adam himself being weak compared to Armin. But nonetheless, they're in a situation where being friends is not exactly possible

Hansen
Adam and Hansen had a great friendship relationship, but ever since Hansen's disappearance, it's unknown.

Andrew Shaw
Andrew and Adam had a rough friendship relationship in season 1, but it started to change after the fight that occurred between Kevin and Armin.

In season 2, Adam started to show more concern towards Andrew himself, and even started to hang out with him a lot, no matter where or when Andrew had gone.

Kevin Adler
The time Adam saw Kevin the first time, he mocked him just for fun. But the moment Adam saw Kevin stood up for himself and got beaten up in a fight, Adam stepped up and helped Andrew carry him to the clinic because he would rather side with Kevin rather than Armin (especially after knowing what Armin could do).

In season 2, Adam started to look at Kevin the same way Andrew did, but with additional offensive jokes sometimes, except the time when Kevin said that his death wouldn't matter to him, causing Adam speechless. Nonetheless, both of them had a great friendship relationship, where Kevin even entrusted Adam with his past (secrecy).

Nate
Both of them met for the first time in season 2, where Adam saw Nate as someone crazier than Armin due to him carrying razor blade. But despite that, Adam did care for Nate's well-being like Andrew did, and he even joked to him many times just to annoy him.